JP2018532576A - Method for separating mill scale from wastewater - Google Patents

Abstract

A method for collecting mill scale from a hot rolling mill is provided. The hot rolling mill includes a ridge. The method includes conveying mill scale particles in the waste water, recovering the waste water from the hot rolling mill dredging, and separating the mill scale particles from the waste water using a separator. A hot rolling mill and a method of modifying the hot rolling mill are also provided.

Description

  The present invention relates generally to the separation of mill scale from waste water of a hot rolling mill or a basic oxygen furnace (BOF).

  Continuous deflection separation (hereinafter “CDS: Continuous differential separation”) is a filtration method for separating contaminants such as solid or particulate matter from a flowing fluid stream. The CDS unit is the most common device used for rainwater treatment. The CDS unit contains a sieve in the top section and sewage in the bottom section. The CDS unit deflects the fluid stream inflow into the separation chamber. The sieve removes contaminants and returns the fluid to the stream. The buoyant solid remains moving in the separation chamber and does not clog the sieve. Heavy solids settle to the bottom of the sewage in the chamber.

  U.S. Pat. No. 7,297,266 intentionally discloses the separation of particles from a fluid stream using a sieving device. The sieve filters relatively large particles from the fluid stream as it passes from the tank storage chamber to the tank outlet. The sieve is preferably of a shape that substantially matches the shape of the switching valve to help smooth the fluid flow in the holding section of the tank.

  U.S. Pat. No. 7,465,391 intentionally discloses an apparatus for separating solid material from a liquid stream using continuous deflection separation. The apparatus includes a cylindrical separation panel that encloses an interior space oriented to have a generally vertical longitudinal axis.

  Hot rolling mills are well known in the steel industry.

  Basic oxygen converters (BOF) are also well known in the steel industry.

US Pat. No. 7,297,266 US Pat. No. 7,465,391

  The present invention provides for recovering the mill scale from the soot in a hot rolling mill or basic oxygen converter to recover the mill scale with low oil contamination.

  The present invention includes a step of conveying mill scale particles in waste water, a step of recovering waste water from a hot rolling mill or a basic oxygen converter dredger, and a step of separating mill scale particles from waste water using a separator. A method for collecting a mill scale from a hot rolling mill or a basic oxygen converter is provided.

  The present invention is connected to a reheat furnace for reheating the steel slab, at least one stand for treating the steel slab downstream of the reheat furnace, and at least one stand for conveying mill scale particles and waste water And a separator for separating mill scale particles from waste water in the basket.

  The present invention may also provide a basic oxygen converter with a separator. The separator may be directly connected to the dehydrator.

  The present invention also provides the use of a separator to separate mill scale particles from waste water, preferably using a coarse particle separator or a continuous deflection separator to collect mill scale. To do.

  The present invention further provides a method for retrofitting a rolling mill that includes the step of placing a separator in the basket. A basic oxygen converter may also be modified using a separator.

The method may also include any of the following features, alone or in combination.
-Collect mill scale particles.
-Wash the collected mill scale.
・ Dehydrate the collected mill scale.
・ Waste water is swirling or flowing at high speed in the cage.
A separator is provided downstream of the reheat furnace, scale breaker, coarse stand, cooling stand, or finishing stand.
・ The separator is located in the basket.
・ The separator is located upstream of the pit.
-The remaining wastewater is directed downstream in the hot rolling mill.
・ The remaining wastewater is directed to the pit.

A hot rolling mill may also include any of the following features, either alone or in combination.
・ A pit downstream of the pass.
The at least one stand is a scale breaker, a coarse stand, a cooling stand, a finishing stand, a cooling or runout table, or a coiler.
-A cleaning device downstream of the separator.
-Dehydrator downstream of the separator.

  Preferred embodiments of the present invention will be described with reference to the following drawings.

1 is a schematic view of a hot rolling mill including a separator according to the present invention. FIG. 3 is another schematic view of a hot rolling mill including a separator according to the present invention. FIG. 3 shows a continuous deflection separator / flow pattern according to the present invention. FIG. 3 shows a continuous deflection separator / flow pattern according to the present invention. FIG. 3 shows a continuous deflection separator / flow pattern according to the present invention. FIG. 3 shows a continuous deflection separator / flow pattern according to the present invention. It is a figure which shows suitable embodiment of the coarse particle separator by this invention. It is a figure which shows suitable embodiment of the coarse particle separator by this invention. It is a figure which shows suitable embodiment of the coarse particle separator by this invention. 1 shows a preferred embodiment of a basic oxygen converter including a coarse particle separator according to the present invention. FIG. 1 shows a preferred embodiment of a basic oxygen converter including a coarse particle separator according to the present invention. FIG.

  The basic oxygen converter (BOF) used in the steel making process produces by-products including filter cake and spark box slurry. Filter cake is usually sent to landfill. Spark box slurry is often carried out.

  In addition, hot rolling mills produce finished steel products from semi-finished steel products including slabs, ingots, billets, and / or blooms, or other long carbon products. The hot rolling mill reheats the semi-finished steel product (slab in this example), rolls the slab so that it is longer and thinner, and winds the length of the steel sheet into a coil for subsequent processing. Solid waste is generated during this process. In addition to filter cake and spark box slurry, this waste, also known as coarse particles or mill scale, is a by-product of the finished steel product. The mill scale is rich in iron and usually contains, for example, more than 70% iron by weight. Mill scale can be an excellent iron resource if it is not contaminated with oil, grease, or other playing card elements. However, high-concentration oil in the mill scale is a major obstacle to recycling the mill scale of the hot rolling mill. Oily mill scale can lead to volatile organic compound (hereinafter “VOC”) emissions violations and cannot be used in sintering and blast furnace ironmaking. Oily mill scale can cause equipment failure and baghouse burning. Oily mill scales are often disposed of in landfills, which can be expensive. Under current market conditions, a clean mill scale is $ 20 per ton higher than an oily mill scale. Clean mill scales are in the form of small bricks and are used in iron and steel making processes. Coarse particles or mill scale can be recycled with benefits. As a result, it is desirable to develop cost-effective techniques for separating coarse particles from BOF wastewater.

  The mill scale is a layer of iron oxide that forms on the surface of the slab. There are two types of mill scales, primary and secondary. The primary mill scale is formed in a reheating furnace, while the secondary mill scale is formed downstream of the reheating furnace, for example, in a roughing mill and a finish rolling mill. Since the temperature in the reheating furnace is about 1200 ° C., even if there is oil, it burns immediately, so the primary scale is generally clean and free of oil. Most mill scales are primary scales formed in a reheat furnace.

ここでΔｍは鋼表面上の形成されたミルスケール層の全質量、Ａはガス雰囲気に関する温度に依存しない係数、Ｔは温度、Ｅは活性化エネルギー、Ｒはガス定数、ｔは経過時間である。 The thickness or mass of the scale layer formed on the steel surface varies with time:

Where Δm is the total mass of the mill scale layer formed on the steel surface, A is a temperature independent factor related to the gas atmosphere, T is the temperature, E is the activation energy, R is the gas constant, and t is the elapsed time. .

  In a hot rolling mill, the steel slab is reheated in a reheating furnace and conveyed to a descaling unit via a hot rolling train. The scale removal unit removes the primary scale from the slab using pressurized water. The spray header can spray 1500 psi of pressurized water onto the slab. A downstream scale breaker roller may be used to grind any remaining scale. A sweep spray may be used to wash away any other loose scale remaining on the surface.

  The slab is then rolled by a roughing mill, trimmed, and descaled again to remove the secondary scale. The secondary scale is, for example, a scale that has grown since the slab exited the furnace for some time in the roughing mill. The high pressure water jet nozzle cleans the scale from the surface of the slab during and after the roughing mill. The slab is then passed through a finishing mill that reduces the thickness of the slab to the desired dimension, and the slab is then cooled and wound into a coil to be ready for transport.

  Oil and grease are present throughout the hot rolling process. The bearing is lubricated with grease and the hydraulic machine operates with oil-containing fluid. The work roll is also lubricated with an oil-containing lubricant. Grease and oil leaking from machinery and rolling mill parts enter the cooling water used during the hot rolling process, resulting in oily wastewater. As this oily wastewater carries the mill scale, the oil sticks to the surface of the mill scale particles and thereby contaminates the mill scale. The oil may be present in an amount greater than 0.15% by weight.

  It is necessary to be able to separate coarse particles or mill scale from the oil. Coarse particle or mill scale separation reduces the cost of waste water treatment and landfill costs for steel hot rolling mills by reducing oily sludge production. Separation also reduces the processing costs of BOF wastewater, and BOF coarse particles are recycled with profit.

  Possible solutions include pre-process separation, post-process separation, and in-process separation. Pre-process separation includes eliminating oil from the hot rolling process or preventing oil from entering wastewater. Post-process separation involves removing oil from oily mill scale and sludge by thermal deoiling, solvent extraction, or intensive washing. In-process separation involves separating mill scale particles from oil and waste water while the waste water is flowing at high speed through the dredging.

  In conventional practice, there were three opportunities for the oil to coat the mill scale particles: (1) counter-movement between the oil and the mill scale in the pit; (2) settled through the floating surface of the oil. Digging the mill scale; and (3) oily foreign matter.

  In-process separation includes advantages over conventional practices. The inventors have found that in scale turbulent water, mill scale particles withstand oil coating. As a result, if the mill scale is taken directly from the flood while the flood is moving at high speed, the mill scale will be clean and recyclable. Therefore, it is desirable to extract a clean mill scale from the soot during separation during the process. Since surplus energy is used, no additional energy is required to separate the mill scale from the oil. Furthermore, no additional environmental protection measures are required.

ここでｃは採取されたミルスケール中の重量％単位での油濃度、ｇ／ｍｍ^２．ｓ単位のｈは廃水の温度および化学的性質に関する係数、ｕはスケールが採取される前の廃水中の重量％単位での油含有量、τはスケールが採取される前のスケール粒子と油滴との間の秒単位での接触時間、およびｍｍ単位のｄおよびｇ／ｍｍ^３単位のｐは採取されたスケールのサイズおよび密度である。 The inventors have found that mill-scale particles can be separated from oil and wastewater “in process” while the wastewater is moving through the basket at high speed according to the following.

Where c is the oil concentration in weight percent in the collected mill scale, g / mm ² . h in units of s is a coefficient relating to the temperature and chemical properties of wastewater, u is the oil content in weight% of the wastewater before the scale is collected, τ is the scale particles and oil droplets before the scale is collected The contact time in seconds between and d and g / mm in mm and p in ³ units are the size and density of the scale taken.

  In the first example, the scale taken from the flood is cleaner than the scale taken by conventional methods where the scale is taken from the pit. Box 1 represents a pit connected to the central fence. Box 2 represents a pit connected to the north side fence, and box 3 represents a pit connected to the south side fence. The mill scale oil concentration from the ridge is about 10 times lower than the scale taken from the pits represented by boxes 1 to 3.

  The inventors have also found that the position of the separator in the mill scale recovery basket is important. Positioning the separator near the source allows for the collection of mill scales with a sufficiently low oil content, such as less than 0.15% by weight. A sufficiently efficient and economical separator should be used to carry out this process. Such a separator may be, for example, a coarse particle separator or a CDS separator, however other types of separators may also be used.

  The separator must be effective, inexpensive and simple. The separator must be able to capture the mill scale from high-speed flooding without contaminating the captured mill scale particles with oil. The separator should not incorporate any additional environmental issues or concerns.

  A coarse particle separator is preferred. For example, International Hydro's HeadCell® coarse particle and sand separator may be preferred. This separator receives wastewater from the soot and separates the wastewater from coarse particles or mill scale and volatile solids. The coarse particles are then washed and dehydrated. The coarse particle separator separates the mill scale from waste water and oil. Since the clean mill scale is then dehydrated, the clean mill scale can be used or sold internally. The wastewater then delivers the oil and the remaining stream to the existing pits and wastewater treatment system.

  In the second example, the oily mill scale was washed with clean turbulent water. The mixture was stirred vigorously for 5 minutes. The scale was allowed to settle over 20 minutes. Water was poured out and scale oil was analyzed. Clean turbulent water removed the oil from the scale.

  In the third example, a scalper device was implemented at the entry point of the first pit. Wastewater enters at high speed. The scalper scoops the scale from the wastewater and drops the scale onto the conveyor. The Scalper Pit Scale produces about 30,000 NT per year and has an oil content of less than 0.05% by weight, while the Pit Scale has an oil content of 0.4% by weight and is about Produces 10,000 NT. The mixture of scalper pit scale and pit scale has an oil content of 0.18% by weight. The ability to recover a clean mill scale reduces the costs associated with oily mill scale and landfill.

  FIG. 1 shows a hot rolling mill 100 according to the present invention. The slab 110 enters the reheating furnace 10 for reheating to a desired temperature such as 1200 ° C., for example. The slab is then transported to the primary scale breaker stand 12 for descaling. The slab 110 continues to the coarse stand 14 and further to the finishing stand 16 before reaching the cooling stand 18 and the coiler 20. The coiled steel is sent out for further processing. For example, coiled steel is sent to cold rollers, pickers, or shipped to another facility.

  Plant reuse water 120 is used to clean and descal the slab 110. Plant reuse water 120 is also used to cool and protect loading rolls and other rolling mill parts. Plant reuse water flow rates may range from 20,000 to 40,000 gallons per minute when used to descal slabs, and compressed water scales at a rate of 3 to 5 feet per second Can be blown away. The plant reuse water and scale are transported to the scale pits 22, 24, 26, and 28 via the troughs 30, 32, 34, and 36, respectively.

  Since the pits 22, 24, 26, and 28 are very wide as compared with the ridges 30, 32, 34, and 36, the water speed decreases and the components in the ridges precipitate. The oil floats up and the scale settles to the bottom. Conventionally, the scale is then recovered from the pit. Care must be taken in the recovery of the scale to avoid contaminating the scale with oil.

  According to the present invention, the scale may be taken from the troughs 30, 32, 34, 36 before it reaches the pits 22, 24, 26, 28. The inventors have found that it is possible to collect a cleaner scale by collecting the scale directly from the basket while the water is flowing. The inventors have also found that it is possible to collect a clean scale by collecting the scale as close as possible to the scale forming source.

  According to a preferred embodiment of the present invention, separators 40, 42, 44, 46 connected to the troughs 30, 32, 34, 36 are used to collect the scale. Separators are well known and are used for rainwater treatment. The separator separates the liquid from the solid material. A HeadCell (R) coarse particle separator manufactured by International Hydro is preferred.

  FIG. 2 shows the heat including separators 40, 42, 44, 46 connected to the troughs 30, 32, 34, 36, used for taking scale “in process” during hot rolling mill operation. It is another schematic diagram of the hot rolling mill 101. The same reference numbers as in FIG. 1 are used to indicate similar components.

  Coarse particle separators and “CDS” separators handle a wide range of rainwater streams and conditions. These techniques employ several major purification processes to remove contaminants from storm water streams with very small footprint, including deflection sorting / filtration, vortex concentration, diffusional precipitation, and rectification.

  3-6 illustrate a separator 40, such as a CDS separator, and a flow pattern. Wastewater enters the deflection separation chamber 204 in a tangential direction through the inlet 202, but a plurality of inlets 202 may be provided. The inlet 202 is located above a cylindrical sieve 206 that is located above the sewage 208 and spaced therefrom by a separation slab 210.

  The flow is smoothly introduced along the circumference of the stainless steel screen 206. A balanced set of hydrodynamic forces are generated in the separation chamber 204 to provide a continuously moving flow across the steel sieve surface 206 to prevent any clogging and to prevent solids through continuous deflection separation and vortex concentration separation. Establish the hydraulic system necessary to separate things.

  Sieve 206 separates solid material, and sewage 208 provides deposit storage space below separation chamber 204. The continuous deflection separation process generates a low energy rest zone 203 in the center of the vortex chamber 204, which is different from typical vortex separation processes. In a simple gravity-based vortex system, the rotational speed increases as you approach the center of the unit. The static zone within the CDS unit allows for effective precipitation of particulates through a much wider range of flow rates than can be achieved using a simple precipitation tank with the same footprint. Particles contained in the deflected process stream are retained by the deflection sorting chamber 204 and maintained in a circular motion that decays at the center of the unit. The dense particles (specific gravity> 1) eventually settle into sewage 208 located below the separation chamber 204. Sewage 208 is isolated from the separation chamber 204 by the separation slab 210 at the bottom of the separation chamber, thereby forming a hydraulic shear surface to minimize the effects of refining. Contaminants trapped in the sewage 208 are isolated from the high speed bypass flow through the unit to prevent refining losses of the trapped contaminants.

  The mill scale particles are affected by the circular motion of the plant water stream 120 in the chamber 204 that forces the particles to move outward toward the sieve 206. Sieve 206 prevents mill scale particles from moving out of chamber 204. Tangential inflow 120 causes rotational movement in separation chamber 204 that is balanced to exceed the radial flow rate through sieve 206. The continuous motion within the separation chamber 204 ensures that the tangential force on the particle continues to rotate the particle and is greater than the radial force produced by the flow through the sieve.

  The turbulent boundary layer at the sieve surface 206 prevents small particles from passing through the sieve 206. The configuration and orientation of the sieve 206 deflects the particles towards the center of the sieve chamber where the resting zone (stagnation core) 203 is present. This impedance generated by the turbulent boundary layer 205 and the deflection force helps to overcome the centripetal force on the entrained particles encased in the separation chamber 204 with a sieve. This turbulent boundary layer and deflection force allow the CDS system to hold particles more effectively than the classic smooth wall vortex concentrator. In comparison, gravity-based smooth wall vortex concentrators rely primarily on toroidal forces to separate solids from the liquid in the vortex chamber. These toroidal forces are present in the same or more in the CDS unit.

  The treated water travels through the cylindrical surface area 206 of the sieve and then exits the separation chamber 204 through the outlet 212. This is a very large channel area, resulting in a very low exit velocity. This low bottom flow greatly enhances the separation capability of the CDS solids separation process beyond that of a basic smooth cylindrical wall vortex unit. In addition to the rest area 203 in the center of the vortex separation chamber 204, a low flow velocity is also generated in the annular space 207 behind the sieve. The flow through the separation screen 206 is highly dispersed. After passing through the sieve surface 206 and entering the annular space 207, the flow is extremely slow compared to the inlet 202, separation chamber 204, and outlet 212 velocities. Static settling takes place in this annular space 207 before the flow 120 moves under the oil control plate 214 and exits the unit 40.

  The toroidal flow motion in the separation chamber of the CDS unit is shown as a circular streamline (FIG. 5). These toroidal flow forces are perpendicular to the horizontal rotational flow at the sieve surface 206 and help move the particles to the center 203 of the CDS processing chamber 204 where the particles later settle into the sewage 208.

  7-9 illustrate a preferred embodiment of the present invention, which includes the use of a separator 40 that is a coarse particle separator 300. The coarse particle separator 300 may be, for example, a HeadCell (R) from Hydro International, or other related processing equipment, including, for example, GritSnail (R) and SpiraSnail (R), both from Hydro International. Also good.

  Coarse particle separator 300 is located in basket 30, 32, 34, 36, see for example separators 40, 42, 44, 46 (FIG. 1). The coarse particle separator 300 is used with a dehydrator 316. Coarse particle separator 300 captures, cleans, and removes fine coarse particles, exfoliation, and dense solids from waste water containing iron rich mill scale.

  Each coarse particle separator 300 includes a displacement header 310 through which inflow (coarse particles, volatile solids, oil, and wastewater) 302 enters the separator 300. The inflow 302 enters the sedimentation tray 308 in a tangential direction via the distribution header 310. The inflow 302 is evenly divided between the different trays 308, thereby establishing a rotating flow pattern and maximizing the contact of coarse particles against the surface area of the tray 308. Coarse particles 303 fall into the bottom stream collected sewage 306 at the bottom of the separator 300 via gravity. The waste liquid 304 from which coarse particles have been removed leaves the chamber through a weir located on the wall 312 of the chamber 301. The discharged waste liquid 304 with coarse particles removed carries oil and other streams downstream to the pits 22, 24, 26, 28 (FIG. 1) for processing by the wastewater treatment system.

  The separated coarse particles / mill scale 303 exits the separator 300 via the collected sewage 306 and is sent to the dehydrator 316 for dehydration. FIG. 9 shows the dehydrator 316. The dehydrator may include those manufactured by Hydro International, such as GritSnail (R) and SpiraSnail (R). The dehydrator 316 includes a tank 318 that contains the washed coarse particles from the cleaning device 314. The conveyor 326 moves the coarse particles 330 from the tank 318. The conveyor includes a rinse spray bar 322, a coarse particle leveler 324, a tail roll rinse 328, and a motor 320. Clean dry coarse particles 330 ′ are output from the dehydrator 316. Clean dry coarse particles 330 'may be used internally or sold at a higher price than contaminated or oil-containing coarse particles. By separating clean mill scale from the wastewater in the basket, clean mill scale can be produced, used internally, or sold. In addition, the processing costs are reduced because less solids reach the pit and wastewater treatment system.

  The separator may also be incorporated into a basic oxygen converter to separate steelmaking wastewater. In BOF, separators, and for example HeadCell® separators, replace existing coarse particle separators, thereby reducing costs. The HeadCell (R) separator is connected directly to the dehydrator, eliminating the need for a pump.

  FIG. 10 shows a BOF system 400 that includes a BOF 402 and a fully wet BOF off-gas cleaning system. In this type of system, the BOF off-gas is cleaned only with water. Coarse particles in the wastewater are often captured via the desilter 410 or hydrocyclone 408. The problem with decylters and hydrocyclones is low efficiency and lack of dehydration. According to a preferred embodiment of the present invention, the coarse particle separator 40 is used in the BOF system 400. The coarse particle separator 40 may replace decylter and / or hydrocyclone. The coarse particle separator 40 can extract coarse particles from waste water and dehydrate coarse particles. For this reason, the use of the coarse particle separator can reduce the amount of waste to be brought to the landfill, and can overcome two disadvantages associated with decylter and hydrocyclone.

  FIG. 11 shows a BOF system 500 that includes a BOF 502 and a spark box wastewater treatment 504. The spark box 504 cools the gas released from the BOF 502 by spraying water toward the gas. Coarse particles and other waste materials are usually collected and transported to a purifier or trailer and slag pan. According to the present invention, the coarse particle separator is used to treat flowing turbulent wastewater. The coarse particle separator 40 can separate clean scale from waste water more efficiently than collecting waste as was known in the past.

  The spark box wastewater treatment may be a wet dry offgas cleaning system or a fully wet offgas cleaning system. Under the spark box 504, waste water is currently collected using a container such as a trailer or a slag pan. Solids settle and water overflows. After some time, the container is carried out and the solids are discarded elsewhere. This practice often ends up with low efficiency, high cost, and messy floor environments. The use of coarse particle separator 40 instead of a container can have the advantages of low cost, high efficiency, and environmental integrity.

  The inventors have recognized that known separators in rainwater treatment and residential wastewater treatment can be modified or optimized for use in hot rolling mills. For example, separators must be adapted for large scale industrial applications in the steel industry. The amount of scale is large and must be continuously conveyed, while current separators are used to handle rainfall and are not continuously used. In addition, there is no need to worry about suspended solids, which are fragments that float above the flow. Furthermore, it is desirable that the oil contaminated with the plant reuse water continues to flow downstream with the plant reuse water. Oil accumulation is undesirable in the separator.

  The separator components, including the sieve, must be optimized to fit the scale size and to fit the existing folds. Mill scale is heavier than sand, for example, scale density is about 5.0 and sand density is about 2.0. Separator components should also utilize materials that are resistant to abrasion by mill scale, oil, and plant reuse water.

  The present invention may also be incorporated into hot rolling mills for other metal products such as copper and aluminum. The present invention also includes retrofitting existing hot rolling mills or basic oxygen converters by placing a separator in the rolling mill cage.

  Using a separator in the soot to separate coarse particles and mill scale from wastewater will reduce capital and operating costs.

  In the foregoing specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. However, it will be apparent that various modifications and changes may be made without departing from the broad spirit and scope of the invention as set forth in the claims below. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims (17)

A method of taking a mill scale from a hot rolling mill, wherein the hot rolling mill includes firewood,
Conveying mill scale particles in waste water;
Recovering the wastewater from the hot rolling mill dredge;
Separating mill scale particles from wastewater using a separator;
A method comprising:   The method of claim 1, wherein the separator is a coarse particle separator.   The method of claim 1, further comprising collecting mill scale particles. The method according to claim 3, further comprising the step of dewatering the collected mill scale.   The method of claim 1, wherein the wastewater is fast and turbulent or flowing in the dredging.   The method according to claim 1, wherein the separator is provided downstream from the reheating furnace, the scale breaker, the coarse stand, the cooling stand, or the finishing stand.   The method of claim 1, wherein the separator is located in a basket.   The method of claim 1, wherein the separator is located upstream of the pit. The method of claim 1, further comprising directing the remaining wastewater downstream in the hot rolling mill.   The method of claim 9, wherein the remaining waste water is directed to the pit. Mill scale

Separated from wastewater according to where
c is the oil concentration in weight percent in the collected mill scale,
g / mm ² . h in s is a coefficient,
u is the oil content in weight% of the wastewater before the mill scale is collected,
τ is the contact time in seconds between scale particles and oil droplets before the scale is taken, and d in g and g / mm ³ p is the size and density of the scale taken
The method of claim 1. A reheating furnace for reheating the steel slab;
At least one stand for processing the steel slab downstream of the reheating furnace;
A tub connected to at least one stand for conveying mill scale particles and waste water;
A separator in a basket for separating mill scale particles from wastewater;
Hot rolling mill equipped with.   The hot rolling mill according to claim 12, further comprising a pit downstream of the ridge.   The hot rolling mill according to claim 12, wherein the at least one stand is a scale breaker, a coarse stand, a cooling stand, a finishing stand, a cooling and runout table, or a coiler.   The hot rolling mill according to claim 12, further comprising a cleaning device downstream of the separator.   The hot rolling mill according to claim 12, further comprising a dewatering device downstream of the separator. A method of retrofitting a hot rolling mill containing a hoe, further comprising the step of placing a separator in the hoe.

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